1. Field of the Invention
This invention relates to cholinergic receptor agonists and antagonists and their use as antinociception (pain relief) agents and as agents for the treatment of a variety of neurologic and psychiatric disorders. In particular, the invention relates to novel classes of azaadamantanes and azanoradamantanes.
2. Summary of the Related Art
The compounds of the invention have uses as cholinergic agonists and antagonists. As such they will have utility in modifying states where there is an imbalance in cholinergic function. An example of cholinergic deficiency is in Alzheimer""s disease where there is degeneration of cholinergic neurons within the CNS. The postsynaptic muscarinic receptors in the forebrain and hippocampus persist and, therefore, muscarinic agonists have utility in treating AD by halting its progression and improving cognitive function. Cholinergic agonists also have utility in the treatment of other CNS disorders including schizophrenia or schizophreniform conditions, mania, bipolar disorders, depression and anxiety. Cholinergic agonists are particularly useful as analgesic agents and, therefore, have utility in the treatment of severe and chronic pain. Cholinergic agonists also have utility in alleviation of intraocular pressure such as found in glaucoma.
Many peripheral disease states have a basis in exaggerated cholinergic drive. Cholinergic antagonists therefore have utility in these conditions. Examples where muscarinic antagonists have utility are in bladder dysfunction, gastrointestinal motility disorders and obstructive airway disease such as COPD and asthma.
In particular, there has been considerable effort in the scientific/medical community to develop non-opiate painkillers which maintain the efficacy of opiates against severe and chronic pain but are devoid of the opiate liabilities of respiratory depression, constipation and dependence. The studies undertaken by various authors and researchers have demonstrated the importance of highly selective muscarinic agonists for use in antinociception (the treatment of pain) without the attendant undesirable side effects. The advantage of having a selective muscarinic agonist for blocking pain has been described in numerous publications. See for example, Sauerburg et al, Life Sci. 56, 807-814 (1995); Naguib et al., Anesth. Analg. 85, 847-85 (1997); Eglen and Watson, Pharmacol. Toxicol. 78, 59-68 (1996).
Jeppesen et al. WO 97/36906, entitled xe2x80x9cHeterocyclic Compounds and their Preparation and Use,xe2x80x9d discloses compounds comprising an unsubstituted azatricyclic heptane attached directly to a substituted or unsubstituted aromatic heterocyclic group which is a 1,2,5-thiadiazole. The compounds are claimed to be useful in treating central nervous system (xe2x80x9cCNSxe2x80x9d) diseases caused by malfunctioning of the muscarinic cholinergic system.
Macleod et al. WO 92/11261, entitled xe2x80x9c4-Azatricyclo[2.2.1.2,6] heptanes and Pharmaceutical Compositions,xe2x80x9d discloses compounds comprising an unsubstituted azatricyclic heptane attached directly to a substituted or unsubstituted 5-membered aromatic heterocyclic group comprising two or three heteroatoms, at least one of which is nitrogen and another of which is oxygen or sulfur. Preferred aromatic heterocyclic groups include a 1,2,4-thiadiazole and a 1,3,4-thiadiazole. The compounds are claimed to be useful in treating neurological and mental illnesses whose clinical manifestations are due to cholinergic deficiency.
Sauerberg et al. U.S. Pat. No 5,578,602, entitled xe2x80x9cCertain 1-Azabicyclo[3.3.1]nonene Derivatives and Their Pharmacological Uses,xe2x80x9d discloses compounds comprising a substituted or unsubstituted azabicyclic ring comprising from between four to ten total atoms attached directly to a substituted or unsubstituted 5-membered aromatic heterocyclic group which is a 1,2,5-thiadiazole or a 1,2,5-oxadiazole. Preferred embodiments illustrate azabicyclic rings comprising 1-azabicyclo[3.3.1]nonene, 1-azabicyclo[3.2.3]octane, 1-azabicyclo[2.2.2]octane, or 1-aza-bicyclo[2.2.1]heptane. The compounds are claimed to be useful as muscarinic agonists.
Sauerberg et al. U.S. Pat. No 5,641,791, entitled xe2x80x9cHeterocyclic Compounds and Their Preparation and Use,xe2x80x9d discloses compounds comprising a substituted or unsubstituted azabicyclic octane attached directly to a substituted or unsubstituted 5-membered aromatic heterocyclic group which is a 1,2,5-thiadiazole or a 1,2,5-oxadiazole. The azabicyclic ring is 1-azabicyclo[2.2.2]octane. The compounds are claimed to be useful as muscarinic agonists.
Georgiev et al. U.S. Pat. No 4,739,074, entitled xe2x80x9cAdamantane Spiro-Pyrrolidene Derivatives,xe2x80x9ddiscloses compounds comprising an unsubstituted tricyclic decane attached directly to a substituted or unsubstituted 5-membered non-aromatic heterocyclic group comprising one heteroatom which is nitrogen. The compounds are claimed to exhibit anti-Parkinson""s activity.
Olesen et al., entitled, xe2x80x9c3-(3-alkylthio-1,2,5-thiadiazol-4-yl)-1-azabicycles. Structure-activity relationships for antinociception mediated by central muscarinic receptors,xe2x80x9d discloses, as the title indicates, compounds of the structure: 
wherein n is 1 (azanorbornanylthiadizoles) or 2 (quinuclidinylthiadiazoles) and R is alkyl, that show high affinity for muscarinic receptors and induce antinociception in vivo.
Shannon et al., entitled xe2x80x9cIn Vivo Pharmacology of Butylthio[2.2.2] (LY297802/NNCC11-1053). An Orally Acting Antinociceptive Muscarinic Agonistxe2x80x9d discloses (+)-3(S)-3-[4-butylthio-1,2,5-thiadiazol-3-yl]-1-azabicyclo[2.2.2]octane. This compound was selected for further study based on the results presented in the Olesen et al., supra. Shannon et al. suggests that this azabicyclo compound may be a selective M4 receptor agonist.
Despite the work done to date in the field there remains a need for antinociceptive agents.
The present invention brings a solution in the form of novel products that are useful as cholinergic receptor agonists and antagonists. In a preferred embodiment, the compounds of the invention can act selectively on certain muscarinic receptors, particularly on M4 receptors, with reduced cholinergic side effects. Consequently, they are well-suited for therapeutic use in the treatment of pain and other neurologic and psychiatric disorders. The compounds of the invention are members of novel classes of azaadamantanes, azanoradamantanes and azahomoadamantanes.
In addition, the invention provides pharmaceutical compositions comprising the compounds of the invention and methods of treating pain and neurologic and psychiatric disorders with the pharmaceutical compositions.
All patent applications, patents, and other publications recited herein are hereby incorporated by reference in their entirety.
The Compounds
The novel compounds of the invention are azacyclic ring systems having the formula I 
including geometrical isomers, enantiomers, diastereomers, racemates, acid addition salts, salts thereof with a pharmaceutically acceptable acid, and prodrugs thereof, wherein 
X is CH2,NH, O or S;
V, W, Y and Z independently are CH or N;
n and m independently are 0, 1, 2, 3 or 4;
R1 and R2 are at any position on the azacyclic ring, including the point of attachment of the heterocycle Q, and independently are hydrogen, xe2x80x94OH, halogen, xe2x80x94NH2, carboxy, straight or branched C1-10-alkyl, C1-10-alkenyl, or C1-10-alkynyl, straight or branched C1-10-alkoxy, or straight or branched C1-10-alkyl substituted with xe2x80x94OH, xe2x80x94CN, xe2x80x94CHO, xe2x80x94OH, xe2x80x94OR3, xe2x80x94SR3, xe2x80x94NH2, xe2x80x94NHR3, xe2x80x94NR3R4, xe2x80x94NO2, xe2x80x94SOR3, xe2x80x94SO2R3, xe2x80x94COR3, xe2x80x94CO2R3, xe2x80x94CONH2, xe2x80x94CONHR3, xe2x80x94CONR3R4, or xe2x80x94CHxe2x95x90NOR3; or
R1 and R2 independently are phenyl, phenoxy, benzoyl, benzyl or benzyloxycarbonyl, each of which is unsubstituted or substituted with halogen, xe2x80x94CN, C1-10-alkyl, C1-10-alkoxy, or C1-10-alkylthio;
R is hydrogen, halogen, xe2x80x94CN, xe2x80x94CHO, xe2x80x94OH, xe2x80x94OR3, xe2x80x94SR3, xe2x80x94NH2, xe2x80x94NHR3, xe2x80x94NR3R4, xe2x80x94NO2, xe2x80x94SOR3, xe2x80x94SO2R3, xe2x80x94COR3, xe2x80x94CO2R3, xe2x80x94CONH2, xe2x80x94CONHR3, xe2x80x94CONR3R4, or xe2x80x94CHxe2x95x90NOR3; or
R is phenyl, phenoxy, benzoyl, benzyl or benzyloxycarbonyl, each is which is unsubstituted or substituted with halogen, xe2x80x94CN, C1-15-alkyl, C1-10-alkoxy, or C1-10-alkylthio; or
R is a 5 or 6 membered saturated, partly saturated or aromatic heterocyclic ring containing one to three heteroatoms; and
R3 and R4 independently are straight, branched, or cyclic C1-15-alkyl, C2-15-alkenyl, C2-15-alkynyl, or combinations thereof, or R3 and R4 independently are phenyl, phenoxy, benzoyl, benzyl or benzyloxycarbonyl groups, each of the foregoing of which are unsubstituted or substituted with H, halogen, xe2x80x94CN, C1-15-alkyl, C1-10-alkoxy, C1-10-alkylthio, or aryl; or
R3 and R4 independently are 5 or 6 membered saturated, partly saturated or aromatic heterocyclic rings containing one to three heteroatoms.
In a preferred embodiment both m and n are 1 in structural formula I and the compounds of the invention have the structural formula: 
wherein 
X is S,
Y and Z are N, and
R is OR3 or SR3.
In a particularly, preferred embodiment of the compounds of structural formula II, R3 is xe2x80x94CH3, xe2x80x94CH2CH3, xe2x80x94CH2CH2CH3, xe2x80x94CH2CH2CH2CH3 or xe2x80x94CH2CH(CH3)2.
The compounds of the present invention (i.e., Formulas I and II) are particularly useful to induce analgesia by selective agonism of the muscarinic M4 receptor. They are useful both in vivo (e.g., for the treatment of pain in mammals, preferably humans, in need thereof) as well as in vitro (e.g., to study the role of muscarinic M4 receptors in biological processes).
Definitions
Except as otherwise expressly indicated, the following definitions are employed herein:
The term alkyl refers to a saturated straight, branched, or cyclic (or a combination thereof) C1-10 hydrocarbon and specifically includes, but is not limited to, methyl, ethyl, propyl, isopropyl, cyclopropylmethyl, cyclobutylmethyl, butyl, isobutyl, t-butyl, pentyl, cyclopentyl, isopentyl, neopentyl, hexyl, isohexyl, cyclohexyl, 3-methylpentyl, 2,2-dimethylbutyl, 2,3-dimethylbutyl, heptyl, octyl, nonyl, and decyl.
The term lower alkyl, as used herein, refers to a C1 to C6 saturated straight, branched, or cyclic (in the case of C6) hydrocarbon, and specifically includes, but is not limited to, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, cyclopropylmethyl, pentyl, cyclopentyl, cyclobutylmethyl, isopentyl, neopentyl, hexyl, isohexyl, cyclohexyl, 3-methylpentyl, 2,2-dimethylbutyl, and 2,3-dimethylbutyl.
The term alkylamino refers to an amino group that has an alkyl substituent.
The term alkynyl refers to a C2 to C10 straight or branched hydrocarbon with at least one triple bond.
The term lower alkynyl refers to a C2 to C6 alkynyl group, specifically including, but is not limited to, acetylenyl and propynyl.
The term aryl refers to phenyl, substituted phenyl, or heteroaryl (as further defined below) wherein the substituent is halo, alkyl, alkoxy, alkylthio, haloalkyl, hydroxyalkyl, alkoxyalkyl, methylenedioxy, cyano, C(O)(lower alkyl), carboxy, CO2alkyl, amide, amino, alkylamino and dialkylamino, and wherein the aryl group can have up to 3 substituents.
The term halo, as used herein, includes fluoro, chloro, bromo, and iodo.
The term aralkyl refers to an aryl group with an alkyl substituent.
The term alkaryl refers to an alkyl group that has an aryl substituent, including benzyl, substituted benzyl, phenethyl or substituted phenethyl, wherein the substituents are as defined for aryl groups.
A heteroatom is N, S, or O.
The term heterocyclyl, heterocyclic, heterocycle and variations thereof mean a cycloalkyl moiety substituted in the ring by one or more heteroatoms. Examples of heterocycles include, but are not limited to, pyrrolidinyl, piperidinyl, and piperazinyl.
The terms heteroaryl and heteroaromatic, as used herein, refer to an aromatic moiety that includes at least one heteroatom in the aromatic ring. Examples include, but are not limited to, furyl, pyridyl, pyrimidyl, thienyl, isothiazolyl, imidazolyl, pyrazinyl, benzofuranyl, quinolyl, isoquinolyl, benzothienyl, isobenzofuryl, pyrazolyl, indolyl, isoindolyl, benzimidazolyl, purinyl, carbazolyl, oxazolyl, thiazolyl, isothiazolyl, 1 ,2,5-thiadiazolyl, isooxazolyl, pyrrolyl, pyrazolyl, quinazolinyl, pyridazinyl, pyrazinyl, cinnolinyl, phthalazinyl, quinoxalinyl, xanthinyl, hypoxanthinyl, pteridinyl, 5-azacytidinyl, 5-azauracilyl, triazolopyridiriyl, imidazolopyridinyl, pyrrolopyrimidinyl, and pyrazolopyrimidinyl.
The term organic or inorganic anion refers to an organic or inorganic moiety that carries a negative charge and can be used as the negative portion of a salt.
The term xe2x80x9cpharmaceutically acceptable applicationxe2x80x9d refers to an organic or inorganic moiety that carries a positive charge and that can be administered in association with a pharmaceutical agent, for example, as a counterion in a salt.
The term xe2x80x9cenantiomerically enriched composition or compoundxe2x80x9d refers to a composition or compound that includes at least 95% by weight of a single enantiomer of the compound.
The term pharmaceutically active derivative refers to any compound that upon administration to the recipient, is capable of providing directly or indirectly, the compounds disclosed herein.
The term xe2x80x9cprodrugxe2x80x9d refers to compounds that are rapidly transformed in vivo to yield the parent compound of the above formulae, for example, by hydrolysis in blood. A thorough discussion is provided in T. Higuchi and V. Stella, xe2x80x9cPro-drugs as Novel Delivery Systems,xe2x80x9dVol 14 of the A.C.S. Symposium Series, and in Bioreversible Carriers in Drug Design, ed. Edward B. Roche, American Pharmaceutical Association and Pergamon Press, 1987, both of which are incorporated herein by reference.
Synthetic Schemes
The following synthetic schemes illustrate how compounds according to the invention can be made. Those skilled in the art will be able to routinely modify and/or adapt the. following schemes to synthesize any compound of the invention.
Synthesis of 1-azaadamantane-4-one starting material: 
Synthesis of azaadamantanes from 1-Azaadamantane-4-one: 
As described in the Examples, infra, the following compounds were made by the foregoing schemes:
Synthesis of oxadiazole derivatives from 1-Azaadamantane-4-one: 
Synthesis of 3-Azanoradamantane-9-one:
See, Bok et al., Heterocycles 12, 343 (1979); Speckamp et al., Tetrahedron 27, 3143 (1971); and Bok et al., Tetrahedron 35, 267 (1979); and Bok et al., Tetrahedron 33, 787 (1977). 
Synthesis of 3-azanoradamantane-9-one derivatives: 
Synthesis of 3-azanoradamantane-6-one:
See Bok et al., Heterocycles 12, 343 (1979). 
Alternatively, one may employ: 
Synthesis of 3-azanoradamantane-6-(chlorothiadiazole): 
Synthesis of Azahomoadamantanes: 
Pharmaceutical Compositions, Methods of Treatment, and Administration
The compounds of the invention are useful as cholinergic receptor agonists and antagonists. In a preferred embodiment, the compounds of the invention act selectively on the M4 central muscarinic receptors and thereby block pain.
Humans, equine, canine, bovine and other animals, and in particular, mammals, suffering from pain can be treated by administering to the patient an effective mount of one or more of the above-identified compounds or a pharmaceutically acceptable derivative or salt thereof in a pharmaceutically acceptable carrier or diluent to reduce formation of oxygen radicals. The active materials can be administered by any appropriate route, for example, orally, parenterally, intravenously, intradermally, subcutaneously, or topically, in liquid, cream, gel or solid form.
As used herein, the term pharmaceutically acceptable salts or complexes refers to salts or complexes that retain the desired biological activity of the above-identified compounds and exhibit minimal undesired toxicological effects. Examples of such salts include, but are not limited to acid addition salts formed with inorganic acids (for example, hydrochloric acid, hydrobromic acid, sulfuric acid, phosphoric acid, nitric acid, and the like), and salts formed with organic acids such as acetic acid, oxalic acid, tartaric acid, succinic acid, malic acid, ascorbic acid, benzoic acid, tannic acid, pamoic acid, alginic acid, polyglutamic acid, naphthalenesulfonic acid, naphthalenedisulfonic acid, and polygalacturonic acid. The compounds can also be administered as pharmaceutically acceptable quaternary salts known by those skilled in the art, which specifically include the quaternary ammonium salt of the formula xe2x80x94NR+Zxe2x80x94, wherein R is alkyl or benzyl, and Z is a counterion, including chloride, bromide, iodide, xe2x80x94O-alkyl, toluenesulfonate, methylsulfonate, sulfonate, phosphate, or carboxylate (such as benzoate, succinate, acetate, glycolate, maleate, malate, citrate, tartrate, ascorbate, benzoate, cinnamoate, mandeloate, benzyloate, and diphenylacetate).
The active compound is included in the pharmaceutically acceptable carrier or diluent in an amount sufficient to deliver to a patient a therapeutically effective amount without causing serious toxic effects in the patient treated. A preferred dose of the active compound, for all of the above-mentioned conditions is in the range from about 0.01 to 300 mg/kg, preferably 0.1 to 100 mg/kg per day, more generally 0.5 to about 25 mg per kilogram body weight of the recipient per day. A typical topical dosage will range from 0.01-3% wt/wt in a suitable carrier. The effective dosage range of the pharmaceutically acceptable derivatives can be calculated based on the weight of the parent compound to be delivered. If the derivative exhibits activity in itself, the effective dosage can be estimated as above using the weight of the derivative, or by other means known to those skilled in the art.
The methods of the invention comprise administration to a mammal (preferably human) suffering from pain a pharmaceutical composition according to the invention in an amount sufficient to alleviate the pain. The compound is conveniently administered in any suitable unit dosage form, including but not limited to one containing 1 to 3000 mg, preferably 5 to 500 mg of active ingredient per unit dosage form. A oral dosage of 1-500, preferably 10-250, more preferably 25-250 mg is usually convenient
The active ingredient should be administered to achieve peak plasma concentrations of the active compound of about 0.001-30 xcexcM, preferably about 0.01-10 xcexcM. This may be achieved, for example, by the intravenous injection of a solution or formulation of the active ingredient, optionally in saline, or an aqueous medium or administered as a bolus of the active ingredient.
The concentration of active compound in the drug composition will depend on absorption, distribution, inactivation, and excretion rates of the drug as well as other factors known to those of skill in the art. It is to be noted that dosage values will also vary with the severity of the condition to be alleviated. It is to be further understood that for any particular subject, specific dosage regimens should be adjusted over time according to the individual need and the professional judgment of the person administering or supervising the administration of the compositions, and that the concentration ranges set forth herein are exemplary only and are not intended to limit the scope or practice of the claimed composition. The active ingredient may be administered at once, or may be divided into a number of smaller doses to be administered at varying intervals of time.
Oral compositions will generally include an inert diluent or an edible carrier. They may be enclosed in gelatin capsules or compressed into tablets. For the purpose of oral therapeutic administration, the active compound can be incorporated with excipients and used in the form of tablets, troches, or capsules. Pharmaceutically compatible binding agents, and/or adjuvant materials can be included as part of the composition.
The tablets, pills, capsules, troches and the like can contain any of the following ingredients, or compounds of a similar nature: a binder such as microcrystalline cellulose, gum tragacanth or gelatin; an excipient such as starch or lactose, a dispersing agent such as alginic acid, Primogel, or corn starch; a lubricant such as magnesium stearate or Sterores; a glidant such as colloidal silicon dioxide; a sweetening agent such as sucrose or saccharin; or a flavoring agent such as peppermint, methyl salicylate, or orange flavoring. When the dosage unit form is a capsule, it can contain, in addition to material of the above type, a liquid carrier such as a fatty oil. In addition, dosage unit forms can contain various other materials which modify the physical form of the dosage unit, for example, coatings of sugar, shellac, or enteric agents.
The active compound or pharmaceutically acceptable salt or derivative thereof can be administered as a component of an elixir, suspension, syrup, wafer, chewing gum or the like. A syrup may contain, in addition to the active compounds, sucrose as a sweetening agent and certain preservatives, dyes and colorings and flavors.
The active compound or pharmaceutically acceptable derivatives or salts thereof can also be mixed with other active materials that do not impair the desired action, or with materials that supplement the desired action, such as antibiotics, antifungals, other antiinflammatories, or antiviral compounds.
Solutions or suspensions used for parenteral, intradermal, subcutaneous, or topical application can include the following components: a sterile diluent such as water for injection, saline solution, fixed oils, polyethylene glycols, glycerine, propylene glycol or other synthetic solvents; antibacterial agents such as benzyl alcohol or methyl parabens; antioxidants such as ascorbic acid or sodium bisulfite; chelating agents such as ethylenediaminetetraacetic acid; buffers such as acetates, citrates or phosphates and agents for the adjustment of tonicity such as sodium chloride or dextrose. The parental preparation can be enclosed in ampoules, disposable syringes or multiple dose vials made of glass or plastic.
If administered intravenously, preferred carriers are physiological saline or phosphate buffered saline (PBS).
In one embodiment, the active compounds are prepared with carriers that will protect the compound against rapid elimination from the body, such as a controlled release formulation, including implants and microencapsulated delivery systems. Biodegradable, biocompatible polymers can be used, such as ethylene vinyl acetate, polyanhydrides, polyglycolic acid, collagen, polyorthoesters, and polylactic acid. Methods for preparation of such formulations will be apparent to those skilled in the art. The materials can also be obtained commercially from Alza Corporation (CA) and Scios Nova (Baltimore, Md.). Liposomal suspensions may also be pharmaceutically acceptable carders. These may be prepared according to methods known to those skilled in the art, for example, as described in U.S. Pat. No. 4,522,811 (which is incorporated herein by reference in its entirety). For example, liposome formulations may be prepared by dissolving appropriate lipid(s) (such as stearoyl phosphatidyl ethanolamine, stearoyl phosphatidyl choline, arachadoyl phosphatidyl choline, and cholesterol) in an inorganic solvent that is then evaporated, leaving behind a thin film of dried lipid on the surface of the container. An aqueous solution of the active compound or its monophosphate, diphosphate, and/or triphosphate derivatives are then introduced into the container. The container is then swirled by hand to free lipid material from the sides of the container and to disperse lipid aggregates, thereby forming the liposomal suspension.
The following Examples are provided for illustrative purposes only and are not intended, nor should they be construed as limiting the invention in any manner. Those skilled in the art will appreciate that variations and modifications of the following Examples can be made without exceeding the spirit or scope of the invention.